#include<bits/stdc++.h>
using namespace std;
int n,ans;
void f(int x){
	for(int i;i<=x/2;i++){
		ans++;
		f(i);
	}
}
int main(){
	cin>>n;
	f(n);
	cout<<ans;
	return 0;
}

/**************************************************************
	Problem: 1307
	User: chenxuanyi
	Language: C++
	Result: Memory Limit Exceed
****************************************************************/